Rubber heel



May 31, 1938. c. LAMB 2,119,016

RUBBER HEEL Filed Dec. 20, 1957 Patented May 31, 1938 UNITED STATESPATENT' OFFICE 2 Claims.

This invention relates to the orthopedic art and particularly to heelsmade of rubber or other elastic material.

Extensive experimentation has been carried on from time to time with theobject of providing a rubber heel which when used will tend to corrector mitigate the condition of fallen arches commonly known as fiat feet.While engaged for many years in the manufacture of orthopedic rubberheels, I have made an intensive study of this problem, and have notedthat one of the main differences of all these so-ca11ed orthopediccorrective rubber heels has been first that they did not supply asufficient degree of resiliency in the main body of the heel, andsecondly, that they were subject to a relatively rapid wearing down ofthe rear outer corners of the heels. The low degree of resiliencypresent in the main body of most of these heels had a tendency to defeatwhatever advantage there is in a rubber heel in the way of correcting a.tendency towards fallen arches or in relieving such a condition after ithas become acute. I also noted that the rapid wearing down of the rearouter corners of rubher heels generally resulted in rendering thesepractically valueless after a relatively short period of use in so faras any corrective tendency they might have. This is because of the factthat when so worn down the fulcrum point in the heel moves forwardly sothat instead of causing the shoe to pull down and rearwardly themetatarsals of the foot, so that the constrictive action of the tendonsunder the foot would lift the internal cuniform and scaphoidstructure-of the instep upwardly, the shoe would tend in fact to resistthe forward turning movement about the fulcrum in the heel and thetendency would be for the weight of the body to be thrown downwardly onthe instep structure with the ultimate result of straining this.

Beginning with the observation of these facts, I have proceeded by myexperiments to the discovery that a new rubber heel having adequateresiliency in the main body thereof produces a distinctly beneficialeffect resulting from corrective forces applied to the arch structure ofthe foot, tending to produce a high arch. Such a heel continues toproduce this effect, however, only so long as it retains a substantiallyfiat lower surface and a substantially uniform degree of resiliency fromthe extreme rear of the heel to the front thereof.

It is, therefore, an object of my invention to provide an orthopedicrubber heel which shall possess a substantially high degree ofresiliency throughout the main body thereof and which will tend whenused to maintain over a relatively long period of use a substantiallyfiat lower surface.

It is a further object of my invention to provide an orthopedic rubberheel the reaction to use of which is such that this heel will retain asubstantially high degree of resiliency in the rear outer portion of theheel over a relatively long period of use.

Yet another object of my invention is to provide an orthopedic rubberheel, the reaction to use of which will be such as to maintain theoriginal shape of said heel to an extent that the fulcrum about whichthe foot is caused to rock, as this heel engages the ground, ismaintained at a substantially maximum distance rearwardly, as when thesaid heel is new.

The manner of accomplishing the foregoing objects as well as furtherobjects and advantages will be made manifest in the followingdescription taken in connection with the accompanying drawing in whichFig. 1 is a side elevational view of a man striding and with the shoe ofhis foremost foot poised so that a rubber heel thereon is just about toengage the ground.

Fig. 2 is a perspective view of the preferred form of my invention whenembodied in a rubber heel for the right foot.-

Fig. 3 is a rear elevational view of the heel shown in Fig. 2 when thelatter is positioned as when applied to a shoe and is taken on thedirection of arrow 3 in Fig. 2.

Fig. 4 is a front elevational view of the heel shown in Fig. 2, and istaken in the'direction of arrow 4 therein.

Fig. ,5 is a vertical sectional view taken on the line 5-5 of Fig. 2,and which shows the structure of said heel when it is new.

Fig. 6 is a diagrammatic cross-Sectional view similar to Fig. 5 andillustrating the condition thereof after it has been subjected toseveral months wear.

Fig. 7 is a longitudinal sectional view of an ordinary rubber heel afterit has been given a similar amount of wear as that to which the heel ofmy invention was subjected before the latter exhibited a worn conditionas shown in Fig. 6.

In searching for a solution to the problems referred to hereinabove, Idiscovered that the abnormal wearing away of the bottom face 01a rubberheel in the area of maximum wear may be greatly decreased by theprovision of material on the other portions of the lower face of rapidlythan the material used in the area of maximum wear.

As a preferred embodiment of my invention, therefore, I have provided arubber heel III in which the main body ii of the heel is composed ofhighly resilient rubber and which also has a relatively high resistanceto abrasion. The body of rubber ll forms a relatively thick upper layerin the heel ll of substantially uniform thickness throughout the heelexcept opposite the area of maximum wear l2 in which the rubber 0f thebody ll extends downwardly to the lower face of the heel. The balance ofthe lower surface of the heel I0 I have divided into areas It and I, thearea I! being that in which the wear is substantially uniform but lessthan the wear in area l2, and the area I being that in which the wear issubstantially uniform but less than the wear in area i5.

In area II I provide an inlay ll of rubber which is somewhat lessresilient than the body of rubber II and considerably more susceptibleto abrasion. In the area II I provide an inlay ll of rubber which isstill harder than the inlay l1 and which is even more susceptible yet tothe abrasion than the inlay l1. In the manufacture of the heel II thebody II and the inlays I1 and II are The result of the more rapidabrasion of the inserts l1 and I. is illustrated in Fig. 6. Here it isseen that the body ll opposite the area I! has been only very slightlybeveled rearwardly, whereas substantially one-half of the thickness ofthe inlays I1 and "have been worn away. The

eifect of this in contributing towards the attain-- ment of theobjective of my invention has been indicated by drawing lines A-A, BBand C-C in Figs. 5, 6 and '7, which designate respectively the planes onwhich the first pressural contact of the heel is had in placing the footon the ground.

In Fig. 5 which shows the heel III of my invention when this was new itis seen that the plane of contact between the heel and the ground issuch that this contact is maintained up to the place where the ball ofthe foot is entirely on the ground a rotational force is exerted by theresiliency of the rear portion of the heel tending to force the frontportion of the shoe downwardly. The resistance to this force by thenatural tenslng of the tendons beneath the foot and upwardly from thecuniform and scaphoid bones of the arch structure is to distribute theload of the foot between the heel and the ball of the foot and maintainthe arch structure in healthful arched condition free from abnormalstrain.

The location of line BB in Fig. 6 illustrates how in the heel of myinvention the plane of contact between the rear portion of the heel andthe ground is maintained practically up to the time the heel which wouldtend to wear away more the ball of the foot engages the ground evenafter the heel has suffered a considerable degree of wear over arelatively long period of use. At the same time it should also be-notedthat while the highly resilient rubber body H has been worn down in areaof maximum wear l2, this wear has been matched by corresponding wearingdown of the inserts l1 and I8 over the balance of the lower surface ofthe heel so that the ultimate result is to prevent the abnormal bevelingof the rear outer-corner of the heel and to keep the bottom of the heelsubstantially flat. It is clear from this that the beneficial results ofthe flat lower surface of a rubber heel are in my invention retainedthroughout a relatively long use of the heel.

In Fig. 7 I have illustrated an ordinary rubber heel 20 as it appearsafter a considerable period of use, the line 0-0 indicating the plane ofinitial contact between a rear lower face ll of the heel and the ground.This plane is seen to be such as to throw the fulcrum about which theshoe rotates away forward towards the middle of the heel. This effects atendency to rotate the shoe in exactly the opposite direction as a newheel. In

other words the heel 20 after engaging the ground on the plane of lineCC not only exerts no corrective force thereafter on the arch structureof the foot, but on the contrary produces a negative reaction applyingundue strains on the arch.

The foregoing comparison can be demonstrated by anyone by alternatelywearing a pair of shoes having new rubber heels and a pair of shoeswhich are badly run down at the outward rear portions thereof andcarefully noting the exactly opposite reaction obtained.

What I claim is:

1. A heel comprising a body of rubber which includes: a base or upperlayer of relatively high resiliency and abrasion resistance, said baselayer extending down to the lower face of said heel in the area ofmaximum wear; and a lower layer of relatively low resiliency andabrasion resistance covering the areas of less than maximum wear, saidlayers being vulcanized into a unitary body, the resiliency and thepower to resist abrasion of said lower layer decreasing progressively asit extends away from said area of maximum wear and towards an area ofminimum wear.

2. A heel comprising a body of rubber which includes: a base or upperlayer of relatively high resiliency and abrasion resistance, said baselayer extending down to the lower face of said heel in an area ofmaximum wear at the rear outer corner of said heel; and a lower layer ofrelatively low resiliency and abrasion resistance covering the balanceof said lower face, said lower layer comprising two or more sections ofprogressively less resiliency and abrasion resistance than said upperlayer and than each other as said sections increase in distance fromsaid area. the section of least resiliency and abrasion resistance beinglocated in an area adjacent the inner forward corner of said heel, saidlayers being vulcanized into a unitary body.

CHARLES LAMB.

